The present invention relates, in general, to the field of pocketed spring cores.
In general, a pocketed spring core has a plurality of springs which are each supported in a pocket made of flexible material, normally textile material, wherein several springs arranged sequentially in a row form a spring strand extending typically in longitudinal direction of the spring core. The adjoining spring strands are disposed in parallel relationship and have a top and a bottom which are each covered by a cover sheet of flexible material in order to provide a connection of the individual spring strands. The cover sheets are normally glued to the spring strands and are made from a textile material, for example fleece. Also the envelopes of the individual springs are normally made from a textile material. Pocketed spring cores offer essential advantages compared to so-called Bonell spring cores as far a resting comfort is concerned, because the individual springs are supported independently from one another in respective pockets which form an envelope and are predominantly made of a fleece.
Since the provision of the cover sheet results in an adherence of the spring strands and thus of the individual springs, although not directly, problems are encountered with respect to a point elasticity. As a spring is exposed to pressure, also neighboring springs become compressed. In other words, the immediate surrounding area of the spring is directly affected as well as some areas farther away. This spring behavior is counterproductive to an optimum resting comfort.
It would therefore be desirable and advantageous to provide an improved pocketed spring core to obviate prior art shortcomings and to provide a better resting comfort.
According to one aspect of the present invention, a pocketed spring core includes a plurality of springs arranged sequentially in rows to form parallel adjoining spring strands, wherein each of the springs is supported in a pocket made of flexible material, a first cover sheet placed over and connected to the spring strands, and a second cover sheet placed under the spring strands and connected thereto, wherein at least one of the first and second cover sheets has predetermined regions which are opened in a direction transversely to a longitudinal extension of the spring strands by a plurality of slots to thereby form strips.
This configuration of a pocketed spring core according to the present invention significantly improves the point elasticity compared to a closed cover sheet. The cover sheet may be slit across the entire width of the pocketed spring core, whereby the longitudinal extension of the spring strands corresponds overall to the length of the pocketed spring core. The width of the strips resultant by the partition corresponds preferably to the relative distance between the individual pockets and thus the springs accommodated therein, whereby the strips extend in parallel relationship. Of course, it is also possible to partially open the cover sheets across the width of the pocketed spring core as well as also in its length, so that different point elasticities can be realized.
In a pocketed spring core of so-called king size, the areas intended for two users can thus be individually configured and conformed to the individual demands. Hereby, the provision of slots can be omitted in the outer marginal area of the cover sheet as well as also in a center area thereof, while the area defining the resting area is respectively slit.
The point elasticities can be made different across regions not only through selection of the width of the strips and their length, as described above, but also through provision of different hardness by changing the wire strength and/or windings of the springs. Thus, it is possible to provide a greater hardness, in the marginal area of the spring core than in the inner region thereof.
Compared to pocketed spring cores which lack the provision of cover sheets and have spring strands that are directly interconnected, a pocketed spring core according to the present invention has the advantage that a sinking into the gaps between the individual spring strands is precluded. The pocketed spring core according to the present invention thus combines the advantages of the conventional pocketed spring core with cover sheets as well as those of a pocketed spring core without cover sheet. In addition, there is no need to apply additional cover material and upholstery material can sink in as a result of the crossed interconnection between the spring strands, on the one hand, and the strips extending transversely thereto, on the other hand.
As the pocketed spring core according to the invention can be made substantially fully automated, the manufacturing process is very cost-effective.